Spring Boot

Convention-driven Java services.

Spring Boot is taught here in 13 lessons, running from Project setup and your first controller through to Next steps: WebFlux, messaging and native images. Each lesson takes one topic, shows the working code, and links onward to the next, so the course can be read straight through in order.

Lessons

1. Project setup and your first controllerGenerate a project, understand the layout, and get an HTTP endpoint answering within a few minutes.
2. REST controllers and dependency injectionThe HTTP annotations you will use daily, DTOs at the boundary, and constructor injection done properly.
3. Configuration, JPA data access and profilesLayered properties, environment-specific profiles, and a repository layer with the traps called out.
4. Request validation and global error handlingBean Validation on DTOs, custom constraints, one consistent error shape with @RestControllerAdvice, and ProblemDetail responses.
5. JPA relationships, queries and paginationMapping associations, choosing fetch strategies, writing JPQL, projecting DTOs, exposing Pageable, and killing N+1 queries.
6. Schema migrations with Flyway and seed dataVersioned and repeatable migrations, baselining an existing schema, repeatable seed scripts, and a rollback strategy that works.
7. Transactions, locking and concurrencyPropagation and rollback rules, the self-invocation trap, optimistic versioning, pessimistic locks and retry strategies.
8. Securing the API with Spring SecurityThe filter chain, stateless JWT resource servers, method security, password hashing, and the CORS and CSRF decisions you must make.
9. Testing Spring Boot applicationsFull-context versus slice tests, MockMvc, @DataJpaTest, Testcontainers against a real database, and when to mock.
10. Observability with Actuator, logging and metricsExposing the right endpoints, custom health indicators, Micrometer metrics, and structured logs you can actually search.
11. Caching, async processing and schedulingCache abstractions with Caffeine and Redis, correct cache keys, @Async executors that do not lose exceptions, and reliable scheduling.
12. Packaging and deploying a Spring Boot serviceLayered jars, Dockerfiles and buildpacks, externalised configuration, container-aware memory settings and safe rolling updates.
13. Next steps: WebFlux, messaging and native imagesChoosing reactive or servlet, using WebClient correctly, integrating Kafka, building a GraalVM native image, and where to read next.

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